Polyamide textile materials, in particular nylon fibers and yarns, are of great value in the textile industry. Many such commercially available polyamide textile materials are receptive to acid, or anionic dyes. Other commercially available polyamide textile materials show limited or no receptivity to anionic dyes. A manufacturer who utilizes both types of textile materials would at times, depending on his production demands, find it advantageous to be able to convert rapidly an anionic dyeable textile material to a non- or limited anionically dyeable textile material without causing degradation of the textile material and therefore be able to use one polyamide textile material for a number of purposes. Thus, it is desirable to have a rapid, non-degradative method of decreasing an acid-dyeable polyamide textile material's affinity for acid dyes.